Jonathan V. Last sees car seats as part of a “huge constellation of factors in modern life” that “nudge” people toward having fewer children, he said during an interview about his book, What to Expect When No One’s Expecting: America’s Coming Demographic Disaster.

Last said car seats effectively create a small “tax on people who want to have more than two kids” by making it harder to fit three kids into a normal sedan, which encourages parents to buy a larger car. This penalty may not dissuade people who already want more children from having them but it makes it “slightly harder to have big families.”